My paret (or is that you?) assumed that all recessive gens are harmfullor a sign of illness or an genetic illness.
They are not.
Brining some more genetic illnesses as argument implies you make the same mistake.
A genetic mutation resulting in illness is not a "genetic illness" unless the gene's host survives to reproduce. It doesn't require that the parents each pass on a recessive trait to activate the disease in the offspring, cosmic rays can cause it.
Perhaps you would be happier were I to use the terminology "previously non-heritable genetic disorder that is now heritable and incorporated into the human gene pool in general as a result of preventing the death of the host".
That seems a bit of semantic hair splitting, but the point is we routinely engage in technological intervention into these cases today, such as the SIRT1 gene that JDRF funded the discovery of, and which, prior to insulin treatment for T1D, would not have survived into a second generation, and was therefore a self-limiting mutation.
The argument isn't whether we are going to extend human life or not, or whether the resulting extensions are "natural" or not in terms of the population, and speaking to Travis Mansbridge's argument, it's too damn late to make that argument: we've already thrown a stick in the spokes of that wheel, and now it's only a matter of how many sticks and how many wheels, not a matter of "if we can".